Solvent based paints and coatings became popular over the years due to the ability to tailor physical properties depending upon resins and other components used. Among the desirable properties obtainable with solvent coatings are quick drying properties, good water resistance, good film coalescence, and resistance to yellowing.
Recently, it has become recognized that solvent emissions can contribute to atmospheric pollution. Low solvent loading is therefore important to reduce solvent emissions into the atmosphere.
Alkyd resins have been known and used for many years. Such resins have had many desirable properties and have had numerous utilities, especially in coating applications. Unfortunately, such resins have had a serious deficiency in that when they are sufficiently soluble for use in high solid systems, they tend to yellow or to have long drying times in air. In general, such resins have not been suitable for high solids coating formulations with reduced solvent loading while having good drying properties to form non-yellowing, water-resistant coatings having a combination of good hardness and flexibility.
Attempts have been made to overcome such problems, e.g., by incorporation of allyl ethers to reduce yellowing with or without fatty acids or drying oils such as described in numerous publications, e.g., Allyl Ethers in Solventless and Water-Based Coatings, O'Neil et al., J. of the Oil and Colour Chemists Association, Vol. 48, No. 11, pp. 1025-1039, Nov. 1965; The Design of Unsaturated Polyester Resins for Surface Coatings, Jenkins et al., pp. 42-59, January 1961; Air-Drying Oil-Free Polyether-Esters, Chatfield, Paint Technology, April 1962, pp. 17-21; Heat Convertible Polyether Ester Resins, Chatfield, Paint Technology, December 1962, pp. 13-16; UK Patent Application 2,190,672, published Nov. 25, 1987; and European Patent Application 0,234,641, published Sep. 2, 1987; all of which are incorporated herein by reference as background information.
In addition, a number of U.S. Pat. Nos. have issued in the area, e.g., U.S. Pat Nos. 3,355,502; 4,871,807 and 4,997,480 all of which are incorporated herein by reference.
The use of trimethylolpropane diallyl ether, in the prior art, often resulted in poor compatibility with solvents or undesirable hardness, as did significant reduction or elimination of drying oils or drying fatty acid content.
The inclusion of aromatic acids into the polymer could similarly cause problems with increased hardness, while inclusion of significant quantities of polyol often resulted in water sensitivity or solvent incompatibility.